Implanted medical electrode lines (also referred to as “electrodes” for short) have to be positioned in the body of the patient at a suitable point and also fixed sufficiently durably in this position in order to attain the desired therapeutic effects reliably and durably. A multitude of different developments for solving this problem have therefore been provided since the introduction of the first implantable cardiac pacemaker.
In order to fix electrode lines in vessel portions or relatively narrow hollow organs in a precisely positioned manner, electrode lines with impressed curvatures in the distal end region have already been proposed for some time, which, following the implantation and the removal of the guide wire or the stylet, tense up to a certain extent between opposite walls of the vessel or hollow organ on account of the curved profile of said electrode lines. A rather reliable position fixing that is also stable in the long term can thus be achieved. An example of such a construction is described in U.S. Pat. No. 5,925,073.
In this context electrode lines having special inner structures have also been developed, with which a rigidity or flexibility that is variable over the longitudinal extent is to be provided; in this regard see U.S. Pat. No. 6,556,873 or European Patent No. 2 024 014 B1, for example.
Special “CRT electrodes” are implanted in coronary sinus vessels in the region of the left ventricle. To this end, these electrodes have a “passive” fixing of the above-mentioned type, the distal region of the electrode being provided with one or more curvatures. During implantation this curvature is put straight by an internally arranged stylet. If this stylet is withdrawn, the electrode returning into the curved state exerts force onto the vessel inner wall and, thus, anchors the electrode at the desired location thereof.
From a technical viewpoint the following possible implementations of such a solution are known and used:
1. Production of an electrode curvature by annealing an MP35N coil arranged in the line body.
2. Production of an electrode curvature by mechanical deformation (cold forming) of a coil arranged in the line body. This is preferably applied in the case of coradial coils, since here each individual wire has an insulation layer of which the melting point is below the annealing temperature of the coil and, therefore, an annealing process cannot be applied.
3. Production of an electrode curvature by thermal deformation of plastic insulation tubes.
4. Production of an electrode curvature by a silicone part injection molded in a curved mold.
5. Production of an electrode curvature by a silicone injection molded part with tension band.
All of these solutions have certain disadvantages, of which the following are specified here:
Firstly: With use of an ETFE-coated coradial coil, an annealing method cannot be applied. However, in order to form a plurality of poles in a small diameter, the use of such a coradial coil is necessary.
Secondly: The desired angle of curvature and the desired force of curvature are not produced by a mechanical deformation of the coil alone.
Thirdly: With use of silicone it is not possible to provide any subsequent thermal deformation. Silicone is an end-cross-linked material, which can no longer deform after the vulcanizing process. The use of silicone in the distal region of a CRT electrode is of great advantage, since flexibility and fatigue strength of a plastic material are superior for this application.
Fourthly: A silicone injection molded part that is injected in a curved shape does not produce the desired angle of curvature and the descried force of curvature (return force).
Fifthly: Due to the small diameter of an electrode line, only very small wall thicknesses are available for a tension band. Furthermore, a silicone injection molded part with tension band can be produced only in a complicated and complex production method with relatively high error potential.
The present invention is directed toward overcoming one or more of the above-mentioned problems.